I made the switch about 4 years ago - the vocalist left, so the drummer then took over and then eventually he left the band, so having done backing vox, I was left 'holding the baby'. I remember when I started I sucked - not a tuning issue, just needed lots of practice to learn how to play and sing with the right timing. There was no easy remedy, just practice. Now four years on, I can't imagine not fronting the band and I do get compliments on my vocals occasionally, although it's still hard work getting things nailed when starting on a new number.
My advice? No-one learnt how to ride a bike without getting on, trying and sometimes falling off. As long as you're mostly in tune and the timing is mostly right, small errors will iron themselves out over time. Good luck - hope you crack it man.
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